of niagara fails



y 1930. H. c. MARTIN Re. 17,740

' I METHOD OF MAKING ABRAsivE: DISKS" Original Filed March 5, 1920-Remains [22, mo

' UNITED STATES HABRY O. MARTIN, OI NIAGARA FALLS, NEW YORK, ABSIGNOR TOTHE OARBOBUNDW PATENT orrics OOIPANY', OI NIAGARA FALLS, NEW YORK, ACORPORATION OI PENNSYLVANIA nnrnon or MAKING mnnsrvr. nrsxs Originalapplication filed March 5, 1920, Serial No. 863,480. Continued andapplication tiled January, 1888, Serial No. 681,554. Original No.1,567,071, dated'Decembei 29, 1925. Application for reissue illedOctober 88, 1927. Serial No. 229.7li2.

Figures 1 and 2 are sectional views of mold I devices and illustratingsteps in the manufacture of the abrading disks; and

Figure 3 is a perspective view of a. finished disk embodying myinvention.

This application is a continuation of my application, Serial No.363,480, filed Marcho, 1920.

My invention relates to' an improvement in the method of manufacturingabrasive disks,

these disks being of the character used on machines known as diskgrinders for grinding flat surfaces on metals and other materials. Suchdisks usually consist of a paper or cloth backing .or body coated with ado not possess very much durability when called upon to do heavy work.Their usefulness is also to a large degree conditioned upon the degreeof porosity of the abrasive, the porosity being the measure'of the freecutting properties of the material. This is due to the fact that thedegree of porosity controls freedom from glazing use; or in other wordsthe free cutting properties of the disk depend upon the extent to whichthe material ground ofi is kept from lodging in the pores.

of the cutting surfaces.

I have discovered that a very eflicient abrading disk can be made bybuilding an 86 abrading body consisting of abrasive grains boundedtogether by a resinous cement upon .a backing of cloth or paper. Asdescribed in my Patent No. 1,567,071, of which this is a division andreissue in part, such resinous cement may be shellac. Or other resinouscement may be used, preferably a synthetic resin such as a bakelite,which is a phenol coridensation product, as described in my applicationSerial No. 307,259,,filed June 28, 1919.

In the practice of my invention, for example, in the making of a disk, Iemploy a shallow circular mold consisting of an iron bottom plate 2 andan iron ring 3 of the prop- 5 er diameter required for the disk. In thisDIVISIONZB mold, I place a disk 4 of cloth or paper and spread over thisa thin layer from three-sixteenths of an inch to three-fourths of aninch thick of abrasive ains mixed with bonding material, prefera ly inapproximately the proportions by weight of ninety-two parts abrasivegrains and eight parts bonding material, although-the exact proportionsmay be varied somewhat to meet the characteristics desired in theparticular disk being manufactured. Shellac when used should, in genmoldis then taken from the oven and a circular iron plunger, such as.illustrated at 5 in Figure 2, is inserted in the ring 3 u on theabrasive material, and the latter is su jected to pressure of threehundred to five hundred pounds, per square inch, which compresses andagglomerates it. Increasing'the propor-. tion of the bonding materialand the pressure increases hardness and decreases the porosity of thedisk. I have used in practice from eight to ten percent of bond ngmaterial and have varied the agglomerating pressure from three hundredto five hundred pounds, er square inch, to meet the variations inardness that are re uired. The disk is then removed from the mo d andallowed to cool, after which it is baked in an oven at a temperature,preferably of from two hundred and ninety to three hundred dcgrees.Fahrenheit.

If the bakingtemperature does not exceed three hundred degreesFahrenheit, the

paper of cloth backing is not destroyed and is available for the purposeof forming an intermediate layer between the disk and the plate uponwhich the disk is fastened, whenput into actual use.

As a modification of the above described method, I may, however, bake'ata temperature of three hundred and fifty degrees Fahrenheit. Thistemperature destroys the i backing, but toughens and improves theabrasive. I then take a fresh piece of backing ma rial and secure it onto the abrasive disk by means of freshly melted bonding material. Inthis manner, I obtain a combination of the bonding agent and backing inas good a Working condition as if the backing was originallyincorporatedwith the bondin agent;

t will be understood that the backing serves two functions, viz, it actsas a means of holding and carrying the disk body in its first meltedcondition and to strengthen the same until it is transferred to thebaking operation, where it is toughened until it no longer needs suchreinforcement. The secfunction is to form an intermediate layer betweenthe disk and plate, as above stated. Both these functions may beperformed by the modification above described, as well as y the firstdescribed method.

I have found that disks made in accordance with my invention, usingordinary ar-.

tifici'al aluminous abrasives in grits from No.

16 to No. 36, will weigh from 1.9 to 2.3 grams per cubic centimeter. Theapparent density of twograms per cubic centimeter gives a very oodcutting efiiciency, and the disk does not g aze up with the materialbeing ground, but maintains a very; good cutting surface. With apparentdensities of from 1.9 to 2.3 grams per cubic centimeter, the equivalentrosity varies from 47 to 36 percent; and it is important that theporosity should not I be less than 36v percent, in order to 've the freecutting properties above descri ed."

An ordinary bound grinding wheel made up according to the methodsheretofore in.

use with grits of these sizes and grades, has an ap arent density offrom 2.4 to 2.6 grams per on ie centimeter, andif used in the samecutting operation would very quickly glaze and show very poor cuttingefiic ency.

In making such grinding wheels the amount of bonding material and theagglomerating pressure greatly exceed that emplciyed in making-mygrindin disks.

n addition to the increase porosity, the

disks made in accordance with my invention have a uniform texturethroughout so that they will remain eflicient during; their life. Theyalso possess the advantage that they do not crack or chip at the edges.They may be a used either wet or d which is nottrue of a- "much greaterthan material not compressed. -The disks mag.

glued disk. The dis s may be made o any esired grade of hardness to suitthe (par- I an apparent density of about 1.9 to 2.3 grams ticularwork inwhich, they are tobe use While the'disks have sufiicient porosity toprevent glazing, they have sufiicient strength and density to stand upunder'hard usage,

and have a durabilit and cutting efliciency isks made of abrasive alsobe'builtup to any thickness desire which is not practical in makingdisks in abrasive is sprinkled on to the adhesive. The nthetic bondingmaterial gives a good tens i e bond,- and the disks are capaweaker oning materials, such for'example-,

as magnesia cement. The abrasive composition' of the disks isconsiderably more porous,'and hence, structurally not as strong as themore dense shellac bound abrasive wheels containing a greater percentageof shellac and made with-a higher a glomerating ressure. However, thecloth backing o my disks supplies an added tensile strength so, that thecomposite disks are capable o safely operatin at'the high peripheralspeeds now used in 'sk inding. The disks, therefore, combine hi enoughporosity to preventglazing, su cient thickness, strength of bond anddensity to have great durability, and'the necessary tensile strength forhlgh speed grinding machinery.

While I have described in detail. the, preferred embodiment of myabrasive disk and its process of manufacture, it is' to be understoodthat the invention is not limited to all of the described details,'but)may be otherwise embodied'within the scope of the following claims. I

1 claim:

l. The herein described method of making abrasive disks, which consistsin mixing abrasive grains with a sy thetic resinous bonding material,spreading mold upon abackm and applying an agglomerating pressure toshape the disk, and then baking the disk so formed, the abrasive grainsand the bonding material being so proort-ioned and the agglonierat-inpressure being so limited as to give the a rading portion of the disk anapparent density of not over about 2.3 grams er cubic centimeter.

he same in a suitable 2. The herein described method of making per cubiccentimeter. 3. The hereindescribed methodof'making abrasive disks, whichconsists in mixing abrasive-grains with a synthetic resinous bondingmaterial, spreadin the mix in a suitable mold and heating t e mix-to"soften the bonding material, a plying an agglomerating pressure to thea rasive materialand baking I ll aking the article so formed, the

the article so formed and applyin a backing thereto, the abrasive grainsand t e bonding material being so pro rtioned and the agglomeratingpressure ingso limited as to give the abrasive portion of the disk anapparent density of not over about 2.3 grams per cubic centimeter and ofa porosity not less than 36%.

4. The herein described-method of makingabrasive disks, which consistsin mixing abrasive grains witha phenol condensation product bondingmaterial, spreading the same in a suitable mold upon a backing andapplying an agglomerating pressure to shape the disk, andthen baking thedisk so formed, the abrasive grains and the bonding material being sopzoportioned and the agglomerating pressure ing so limited as to givethe abrading portion of'tne disk an apparent density of not over about2.3 grams per cubic centimeter and of a. porosity not less thanapproximately 5. The herein described method of making abrasive disks,which consists in mixing abrasive grains with avphenol condensationproduct, spreading-thesame in a suitable mold upon a backing, placingthe mold in a melting oven and bringing it with its contents to a temrature suflicient to soften the henol con ensation product, and thenapplying an agglomerating ressure to the abrasive material and thenaking the article so formed, the abrasive grains and the phenolcondensation product being so proportioned and the agglomeratingvressure being so limited as to produce a finis ed disk having anabradingportion of an apparent density of about 1.9 to 2.3 grams per cubiccentimeter and of a porosity not less than ap roximately 36%."

6. The herein described method of making abrasive disks, which consistsin mixing abrasive grains with aphenol condensation prod- Iuct,spreading the mix in a suitable mold and heating the mix to softenthe phenol condensation product applying an agglomerating pressure tothe abrasive material and baking the article so formed and applying abacking thereto, the abrasive grains and the phenol condensation productbeing so proportioned and the agglomerating pressure being so limited asto give the abrasive portion of the disk an apparent density of not overabout 2.3 grams per cubic centimeter.

7 The herein described method of making abrasive disks which consists inmixing abrasive grains with a synthetic resinous bonding material, theresinous bonding material forming not over 10% of the mix, spreading thesame in a suitable mold upon a backing, placing the mold in a meltingoven and bringing it with its contents to a temperature sufficient tosoften the resinous bonding material, then applying pressure to the mixto compress and agglomerate it, and then baking the article so formed,substantially as described.

f8. lhe herein described; method of making abrasive disks which consistsin mixing abrasive grains with a synthetic resinous bonding material,spreadin the same in a suitable -mold upon a flexi le backing, placingthe mold in amelting oven and bringing it with.

its contents to a temperature suflicient to soften the bonding material,then applying with its contents to a temperature sullicicnt to softenthe bonding material, then applying an agglomerating pressure to theabrasive material and then baking the article so formed, the abrasivegrains and the bonding material being so proportioned and theagglomeratmg pressure being so limited as to give the finished disk :1porosity not less than about 36%, substantially as described.

10. The herein described method of making abrasive disks which consistsin mixing abrasive grains with a phenolic condensation product, thephenolic condensation product forming not over 10% of the mix, spreadingthe same in a suitable mold upon a backing, placing the mold in amelting oven and brin ing it with its contents to a temperature su cientto soften thepheno-lie condensation product, then applying pressure tothe mix to compress and agglomorate it, and then baking the article soformed, substantially as described.

11. The herein. described method of making abrasive disks which consistsin mixing abrasive grains with a phenolic condensation product, spreadinthe same in a suitable mold upon a fiexi le backing, placing the mold ina melting oven and bringing it with its contents to a temperaturesufiicient to soften the phenolic condensation product. then applying anagglomerating pressure of not over 500 pounds per square inch to thephenolic condensation product to give it the required density, and thenbaking the article phenolic bonding material being so proportioned andthe agglomerating pressure being so limited as to glve the finished disk:1 poros- :gity not less than about 36%, substantially. 5 as described.

In testimony whereof I havehereunto set my hand. 7

HARRY C. MARTIN.

